You should be safe to connect a 3-pin to a 4-pin. As far as I am aware 4-pin connections are for fans with higher power consumption and fan control. You should be fine to have a pin remaining.
Thanks Rich. From what I know the fourth pin is exactly as you said, for more advanced fan control features. My CPU after-market fan has that function, but the standard case fans don't. I purposely bought a case with large (200mm) and quiet fans so I wouldn't need to have control over them.
Do you know if it matter whether I connect the three pin to the left or to the right of the four pin connector? In other words, either I'll have the far left pin exposed or the far right. I don't think it really matter, but figured it wouldn't hurt to ask.
Thanks again for the info